Severe Weather Threat Day 1 Sat Jul 27

A Slow Moving Cutoff Upper Low Will Persist Over The Great Lakes
Region...While Upper Ridge Remains Anchored Over The Swrn States.

Upper Jet Max Now Over Nd Will Move Sewd Into Base Of The Cutoff
Low...Reaching The Oh Valley Saturday Afternoon. Meanwhile...Vort
Max Now Over The Lower Ms Valley Will Weaken As It Continues Ewd
Through Srn Portion Of The Gulf Coast States. Shortwave Trough Over
The Tn Valley Should Deamplify And Weaken As It Ejects Toward The
Cntrl Appalachians.

At The Sfc An Occluded Low Over Srn Ontario Will Weaken As Secondary Cyclogenesis Commences Over Mi Within Exit Region Of Upper Jet Dropping Into Base Of Cutoff Low. This Upper Impulse Will Provide The Impetus For A Cold Front To Accelerate Sewd Into The Oh And Tn Valleys With Trailing Portion Likely To Extend Wwd Into Ks/Ok To A Developing Lee Low Over Sern Co Where It Will Likely Stall.

Meanwhile A Quasi-Stationary Front Will Persist From The Gulf
Coastal States Into Sern Tx.

Cntrl High Plains...

Sely Low Level Winds Should Become Established From Wrn Ks Through Ern Co East Of A Developing Lee Low. This Flow Regime Will Result In Advection Of Richer Moisture /50s Dewpoints/ Nwwd Into The Cntrl High Plains Beneath Steep Mid-Level Lapse Rates. Diabatic Warming Will Result In Further Destabilization With An Axis Of 1000 J/Kg Mlcape Likely From A Portion Of Ern Co Into Wrn Ks. Orographic Forcing Promoted By Diabatic Warming Within Plume Of Higher Pw And Weak Impulses Moving Sewd Through Nrn Periphery Of Upper Ridge Should Result In Storms Developing Over The Mountains. Activity Will Subsequently Spread Sewd Into The High Plains Within A Nwly Flow Regime. Other Storms May Develop Within Zone Of Convergence Along Stationary Front East Of Lee Sfc Low Over Swrn Ks. Effective Shear From 40-50 Kt Will Support Supercells With Isolated Large Hail And Damaging Wind The Main Threats.

Lower Ms Valley...

Mcs Will Likely Be In Progress Early Saturday From Portions Of Cntrl
La Into Srn Ms And Swrn Al In Association With Sewd Advancing Mcv. A
Modest Llj And 30-40 Kt Vertical Shear Will Accompany The Mcv...But
Winds Are Forecast To Gradually Weaken With Time. Widespread Clouds From Convective Debris Should Limit Insolation Which Along With Weak Mid-Level Lapse Rates Suggest The Thermodynamic Environment Will Remain Marginal.

Modest Intensification Of Storms Will Be Possible From Srn Ms...Sern La Into Srn Al With A Threat Of Mainly Isolated Damaging Wind Conditional Upon Sufficient Diabatic Warming. Given The Conditional Nature Of The Threat...Will Maintain 5% Severe Probabilities This Outlook.

Oh Valley And A Portion Of Pa And Ny...

Richer Moisture With Low-Mid 60s Dewpoints Will Advect Through Much Of The Warm Sector Across The Oh Valley And A Portion Of The Nern States. Widespread Clouds Will Limit Insolation...Except Maybe
Portions Of Pa And Ny...Which In Conjunction With Weak Mid-Level
Lapse Rates Should Result In Marginal Instability With Mlcape Likely
To Remain Well Below 1000 J/Kg.

Numerous Showers And Thunderstorms Are Expected To Develop Within The Weakly Capped Warm Sector Where 30-40 Kt Vertical Shear Will Exist. A Few Loosely Organized Bands Of Mostly Multicell Convection And Perhaps Some Mid-Level Rotation May Develop With Some Of The Storms. Some Of The Activity May Become Capable Of Producing Isolated Strong To Damaging Wind Gusts. Given The Expected Marginal Thermodynamic Environment...Will Maintain 5%
Wind Probabilities For Now...But Continue To Monitor For A Possible
Slight Risk In Later Outlooks.


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